Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/42—Polycarboxylic acids; Anhydrides, halides or low molecular weight esters thereof
  • C08G59/4246—Polycarboxylic acids; Anhydrides, halides or low molecular weight esters thereof polymers with carboxylic terminal groups
  • C08G59/4253—Rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S525/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S525/911—Polymer from ethylenic monomers only, having terminal functional group other than unsaturation

Definitions

• Epoxy resins have been widely used for many years in making solid products, including molding compositions and fiber reinforced structural plastics, and also casting or potting compositions, as well as coatings and adhesives. Epoxy resins are particularly advantageous because they are easily converted from liquid or pasty or thermoplastic initial materials into strong and chemically resistant thermoset products, with minimum shrinkage and without evolution of volatile materials. Nevertheless, such compositions tend to be brittle when they are sufficiently crosslinked to exhibit a desirably high heat distortion temperature, and previous attempts to diminish the brittleness and produce a high impact resistance by the usual means, such as introduction of plasticizers or flexibilizers, have not been completely satisfactory because other desirable properties, such as strength, have been sacrificed. Accordingly, an object of this invention is production of thermoset epoxy resin compositions which are not brittle but have a high resistance to impact and crack propagation without reduction of strength.
• a di-epoxy compound is combined with a chain extender, a ross-linking agent, and about 5% (based on the weight of the di-epoxy compound) of a functionally terminated elastomer.
• a chain extender e.g., a chain extender
• a ross-linking agent e.g., a ross-linking agent
• a functionally terminated elastomer elastomer
• the epoxy constituant should contain two terminal epoxy groups as the principal reactive groups.
• Many such materials are known, including di-epoxy ethers of diphenols such as the diglycidyl ether of bisphenol A, di-epoxy esters of dicarboxylic acids such as diglycidyl adipate, and di-epoxy derivatives of dienes such as butadiene dioxide or vinyl cyclohexene dioxide.
• di-epoxy ethers of diphenols such as the diglycidyl ether of bisphenol A
• di-epoxy esters of dicarboxylic acids such as diglycidyl adipate
• di-epoxy derivatives of dienes such as butadiene dioxide or vinyl cyclohexene dioxide.
• dienes such as butadiene dioxide or vinyl cyclohexene dioxide.
• the chain extender may be any of the difunctional materials known to be reactive with epoxy compounds at temperatures substantially above room temperature, such as diphenols, dibasic acids, or dimercaptans.
• diphenols dibasic acids, or dimercaptans
• resorcinol bisphenol A, bisphenol S, azelaic acid, phthalic acid, or m-dithio benzene
• the material used as a chain extender contain only two functional groups, as the presence of three or more functional groups reactive with epoxy groups might result in undesirable premature cross-linking, as mentioned above.
• highly reactive materials of which primary amines and secondary diamines are typical, are not preferred, since they tend to react at room temperature, so that the reaction is difficult to control and the materials remain workable for only a very short time after mixing.
• the cross-linking agents are the materials which, either by direct reaction or indirectly by preliminary decomposition followed by a reaction, are capable of attacking residual functional groups at reasonably elevated temperatures to connect the polymer chains and produce an adequately cross-linked and, therefore, satisfactorily thermoset final product.
• a great many materials known to be hardening or cross-linking agents for epoxy resins are disclosed in the "Handbook of Epoxy Resins" already mentioned.
• Those presently preferred are tertiary or secondary amines or similar nitrogenous bases such as are sometimes designated “Lewis bases”, or their salts, including such widely used materials as tris (dimethylaminomethyl) phenol, piperidine, dicyandiamide, triethylene tetramine, and the like.
• the functionally terminated elastomer may be any of a great many types of linear polymers having a backbone of such a character that it is more or less rubbery or elastomeric at the intended temperature of service of the product, with each chain molecule containing two, or at most, a small number of, groups reactive with epoxy groups.
• This elastomer constituent is preferably one which is compatible with, that is, soluble in, the particular type of epoxy material selected, in its unreacted condition, but having only a limited solubility in the reaction product of the di-epoxy compound with the chain extender, so that it will separate as minute particles or domains of a separate phase.
• the reactive end groups of the elastomer have a reactivity toward epoxy groups not greater than the reactivity of the chain extender.
• the proportion of elastomer should be small, and preferably about 5% based on the weight of the di-epoxy compound, so that it will not significantly decrease the strength or modulus of the matrix material. However, as little as 2 1/2% will give good results, and as much as 7 1/2% may be used without significant loss of strength of the product.
• Such elastomers include functionally terminated chain polymers of various kinds, including polymers of dienes such as butadiene, chlorobutadiene, or isoprene; copolymers of dienes with each other or with ethylenically unsaturated compounds, such as copolymers of butadiene with styrene, acrylonitrile, or ethyl acrylate; butyl rubber; ethylene-propylene rubber; polymers of epichlorohydrin or other polyether elastomers; polysilicones; elastomeric polyamides or polyamines; and the like, in each case with a small number, preferably two, functionally reactive groups, which are preferably the terminal groups of the chain molecule.
• dienes such as butadiene, chlorobutadiene, or isoprene
• copolymers of dienes with each other or with ethylenically unsaturated compounds such as copolymers of butadiene with st
• Suitable functionally terminated elastomers include those having hydroxyl, mercapto, carboxyl, or amino groups, preferably carboxyl or phenolic hydroxyl, at or near the ends of the chain molecules.
• Such materials include amine terminated polyamides, such as nylon finished by reaction with a small excess of a diamine; functionally terminated polyethers such as primary amine terminated poly-tetramethylene-oxide or poly-epichlorohydrin or poly-ethylene oxide; mercapto terminated alkyl acrylate polymers such as copolymers of ethyl acrylate with a little butyl acrylate; carboxyl terminated liquid polymers or copolymers of butadiene or other dienes; and the like.
• the functionally reactive groups be carboxyl or phenolic hydroxyl groups, and if they are either much more or much less reactive than phenolic hydroxyl, to convert them to phenolic hydroxyl or other functional groups of similar reactivity, as will be explained in more detail in the following description.
• the molecular equivalent proportion of chain extender to the di-epoxy compound should be such that free epoxy groups will always be present in large excess until the setting reaction is essentially completed.
• the chain extender be limited to a proportion distinctly less than that equivalent to the di-epoxy compound, and preferably, considerably less than the difference between the number of equivalents of epoxy groups and the number of equivalents of functionally reactive groups in the elastomer. That is, there should be sufficient epoxy material to react with the chain extender, the elastomer, and also the setting agent or hardener. Best results are obtained when the chain extender is in the range of 20% to 60% of equivalency to the di-epoxy compound, and preferably 30% to 50% of equivalency.
• compositions of this invention can undergo a rather far-reaching reaction and change in physical properties without losing their ability to be molded or otherwise shaped to their final form, nor their ability to bond firmly to surfaces of other material when used as coatings or adhesives, and can then be completely converted or set by simply heating at an appropriate temperature for a suitable time. It is also confirmed by the observation that the composition tends to become opaque during the course of the reaction and that particles of a separate phase can be identified by suitable examination of the finished product.
• the products of this invention When properly prepared, the products of this invention exhibit a combination of extremely high strength and modulus with an impact and fracture resistance many times greater than was previously attainable. However, these outstanding results are not attainable unless all four of the specified kinds of ingredients are present in the approximate proportions indicated.
• Liquid epoxy resin which is the di-glycidyl ether of bisphenol A, of average molecular weight 380, and an n value of 0.2 meaning that on an average one out of five molecules contains an additional glycidyl and bisphenol A residue, which results in a pendant hydroxyl in the chain molecule. This is a standard commercial material.
• Bisphenol A which is 2,2' di-hydroxyphenyl propane and is a standard commercial material.
• This is a commercial material sold under the name Hycar CTBN and will be designated as CTBN. It can be prepared by polymerization with azo dicyanovaleric acid initiator as described in Siebert U.S. Pat. No. 3,285,949.
• compositions are prepared containing the following proportions, in parts by weight, with the results indicated:
• compositions In preparing the compositions, all ingredients except the piperidine are thoroughly mixed at 120° to 150° C and the mixture is subjected to a vacuum to remove bubbles. After cooling to below 50° C, the piperidine is carefully mixed in without introducing air bubbles. The mix is then ready for casting, encapsulation, or the like. Test specimens are prepared by casting in a tray lined with poly-tetrafluoroethylene, preheated to 80° C, with brief application of a vacuum if needed for removal of bubbles. The composition is cured 16 hours at 120° C in an oven.
• Compositions A, B, and C have adequate strength and hardness, but their use is seriously limited by their brittleness, indicated by the very low value of fracture energy.
• the fracture energy test and some results obtained with it are described by Rowe, Siebert & Drake in "Toughening thermosets with liquid butadiene/acrylonitrile polymers", Modern Plastics Vol. 47, No. 8, p. 110, August 1970.
• Composition D like those described in the foregoing publication, has a much higher fracture energy than A, B, and C, and is accordingly far less brittle. These are all representative of the prior art.
• Composition E which is representative of this invention, not only has a very much higher fracture energy than any of the prior art compositions, but has higher strength, elongation, modulus, and deflection temperature than composition D, toughened by simple addition of rubber.
• compositions are prepared and tested in the same manner as in Example 1, using liquid rubbers similar to CTBN except that the proportion of acrylonitrile in the rubber is varied, with the following results:
• a phenol terminated rubber is prepared by heating CTBN with a slight excess of bisphenol A in the presence of thionyl chloride.
• CTBN 3200 parts by weight of CTBN are mixed with 260 parts thionyl chloride (somewhat over two molar equivalents based on the CTBN, for reaction with the two terminal carboxyl groups of the CTBN).
• Sulfur dioxide is evolved immediately. Examination of the infrared absorption spectrum shows disappearance of the carboxyl carbonyl bands previously observed in CTBN and appearance of an acid chloride carbonyl absorption band, indicating complete conversion of the carboxyl groups to acid chloride groups. Unreacted thionyl chloride and unvented sulfur dioxide are removed by warming to 50° C and applying a vacuum.
• the intermediate product is mixed with 500 parts bisphenol A (an equimolar proportion with respect to the thionyl chloride used). Hydrogen chloride is evolved, and after the reaction is apparently terminated, a vacuum is applied for removal of remaining hydrogen chloride.
• the infrared spectrum shows disappearance of the acid chloride band and appearance of a new carbonyl band characteristic of a phenol ester.
• the product consists of the original rubber backbone with each terminal carboxyl group esterified by one of the phenolic hydroxyl groups of the bisphenol A and the other phenolic hydroxyl being the new terminal group. It is accordingly a phenol terminated elastomer. It is incorporated into an epoxy composition in the same manner described in Example 1, replacing the CTBN of Example 1-E. Fracture energy is found to be an average of 44 inch pounds per square inch.
• a phenol terminated rubber is prepared by reacting CTBN with a large excess of bisphenol A and a small amount of p-toluenesulfonic acid.
• CTBN a large excess of bisphenol A and a small amount of p-toluenesulfonic acid.
• 1000 parts CTBN are mixed with 300 parts bisphenol A (over 4 molar equivalents based on the CTBN) and one-half part of p-toluenesulfonic acid dissolved in acetone, and heated to 150° C for 2 hours.
• the product when titrated with alcoholic potash shows a reduction of acidity from a value equivalent to 2.70% COOH in the original CTBN to a much smaller value equivalent to 0.74% COOH.
• the infrared spectrum shows a carbonyl absorption band shifted from the previous carboxyl carbonyl band.
• the terminal carboxyl groups in CTBN originate from the azo dicyanovaleric acid initiator which has the cyano group on the third carbon from the carboxyl carbon, it is believed that the cyano and carboxyl groups combine to form a six-membered glutarimide ring with which the bisphenol A forms an adduct, leaving the second phenolic hydroxyl of the bisphenol A as a new terminal group.
• Liquid epoxy resin 100 parts is mixed with 24 parts bisphenol A, 5 parts HTBN (a commercially available liquid rubber which is a hydroxy-ethyl ester of CTBN) and 5 parts piperidine and cured in the manner described in Example 1.
• the fracture energy is 20 to 40 inch pounds per square inch.
• An epoxy terminated elastomer is prepared by dissolving 1000 parts liquid epoxy resin with 800 parts CTBN and 1 part p-toluenesulfonic acid in about 3500 parts benzene and heating under total reflux for six hours, after which the benzene is distilled off.
• the infrared spectrum shows disappearance of the hydroxyl and carbonyl absorption bands and increase in intensity of the ester carbonyl absorption band.
• the product consists of a mixture of unreacted diglycidyl ether of bisphenol A (the main constituent of the liquid epoxy resin used) and the tetra-epoxy ester resulting from esterification of the carboxyl group of the CTBN with the pendent hydroxyl groups of the high molecular weight fraction of the epoxy resin. When this product is mixed with additional epoxy resin, bisphenol A, and piperidine and cured in the manner described in Example 1, a strong non-brittle product results.
• epoxy compounds of various origins can be used in similar ways to replace the diglycidyl ether of bisphenol A, as was previously mentioned.
• Typical materials include mercapto terminated copolymers of isoprene and acrylonitrile, carboxyl terminated polybutadiene or carboxyl terminated copolymers of butadiene and styrene or of isoprene and acrylonitrile, hydroxyl terminated copolymers of butadiene and acrylonitrile, carboxyl terminated poly-acrylic esters, mercapto terminated poly-acrylic esters, functionally terminated polyethers such as amine terminated poly-tetramethyleneoxide or poly-epichlorohydrin or polyethylene oxide, all of which can be incorporated into epoxy compositions of the kinds described with the same good results.
• the improvements of this invention are not simply flexibilizing. Flexibilizing reduces the strength and the modulus of the product, and therefore diminishes the value of products for many purposes where rigidity of maintenance of dimension is important. Here a many-fold improvement in toughness is achieved unexpectedly with essentially no reduction and sometimes even an increase in strength and stiffness.

Landscapes

• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Epoxy Resins (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Priority Applications (12)

Applications Claiming Priority (1)

Related Child Applications (1)

Publications (1)

Family

ID=22781798

Family Applications (2)

Family Applications After (1)

Country Status (11)

Cited By (27)

Families Citing this family (49)

Citations (2)

Family Cites Families (5)

• 0
  • BE BE793030D patent/BE793030A/fr unknown
• 1971
  • 1971-12-20 US US05/210,156 patent/US3966837A/en not_active Expired - Lifetime
• 1972
  • 1972-12-19 CA CA159,377A patent/CA993138A/en not_active Expired
  • 1972-12-19 IT IT70992/72A patent/IT976107B/it active
  • 1972-12-19 DE DE19722262025 patent/DE2262025A1/de not_active Withdrawn
  • 1972-12-20 JP JP12733572A patent/JPS5649931B2/ja not_active Expired
  • 1972-12-20 FR FR727245368A patent/FR2164719B1/fr not_active Expired
  • 1972-12-20 LU LU66707A patent/LU66707A1/xx unknown
  • 1972-12-20 GB GB5893472A patent/GB1408798A/en not_active Expired
  • 1972-12-20 NL NL7217405A patent/NL7217405A/xx not_active Application Discontinuation
  • 1972-12-20 CH CH1871572A patent/CH564042A5/xx not_active IP Right Cessation
• 1976
  • 1976-06-24 US US05/699,218 patent/US4107116A/en not_active Expired - Lifetime

Patent Citations (2)

Also Published As

Similar Documents